60 



FIXING AND HARDENING AGENTS 



temperature, wash out with running water. Much used, especially 

 for nervous tissues. 



MoELLER {Zeit. wiss. ZooL, Ixvi, 1899, p. 85) takes 1 vol. of 

 formol, and 4 of 3 per cent, bichromate (for the intestine of 

 mammals). 



Held (Abk. Sachs. Ges. Wiss., xxxi, 1909, p. 196) takes 3 per 

 cent. sol. of bichromate with 4 per cent, of formol and 5 per cent, 

 of acetic acid (for inner ear). See also Morel and Bassal, Journ. 

 Anat. Phys., xlv, 1909, p. 632, and Helly and Maximow formulae. 

 Look up section on " Mitochondria," especially paragraphs on 

 Regaud and Schridde, §§ 698-702. 



119. Chromic Acid Formol. Lo Bianco fixes marine animals for half 

 to one hour in 10 parts of 1 per cent, chromic acid with 1 of formol and 

 9 ot sea-water, and passes into graded alcohols 



Marchoux (from Perez, Arch. Zool. Exper., v, 1910, p. 11) takes 

 11 parts 1 per cent, chromic acid, 1 of acetic acid, 4 of water, and 16 of 

 formol (added just before using). 



These mixtures are neither so good nor so reliable as Bouin's picro- 

 formol. ^ 



i?i\^°''P" Formol. Nelis {Bull. Acad. Sc. Belg., 1899 (1900), 

 p. 726) fixes spinal ganglia for twenty-four hours in 1 litre of 7 per cent, 

 tormol with 5 c.c. of acetic acid, 20 grm. of cupric sulphate, and sub- 

 limate to saturation. 



Stappers (La Cellule, xxv, 1909, p. 356) used (for Sympoda) a mixture 

 ot GriLSON s : 100 parts of formol of 5 per cent, with 2 gms. of nitrate 

 of copper. 



Strong (Journ. Comp, Neur., xiii, 1903, p. 296) fixes the head of 

 Acanthias by injecting a mixture of equal parts of formol and 5 per 

 cent, solution of bichromate of copper. 



121. Nitric Acid Formol. Wilhelmi {Fauna u. Flora Golf. Neapel, 

 xxxn, 1909, p. 15) fixes Triclads in Apathy's mixture of equal parts of 

 6 per cent, mtnc acid and 6 per cent, formol, and brings them direct 

 into strong alcohol. 



T.^^^^' ^,*^^*<^"^ Formol. Bing and Ellermann {Arch. Anat. Phys., 

 Phys. Ahth., 1901, p. 260) fix medullated nerves in 9 parts of acetone 

 with 1 of formol. 



123. Formic Acid. This substance has been used in the past in a 

 number of fixing fluids, e.g. in Dr. Lindsay Johnson's mixture (§ 50) 

 and has been more recently investigated by Professor Mary J. Guthrie, 

 who informs us {in Uteris) that promising results have been obtained 

 with this acid as a substitute for acetic acid. 



Dr. Guthrie's tests were made because of the information that has 

 been obtained by the ceU physiologists that formic acid penetrates 

 more rapidly and is more toxic than acetic acid. In addition, fatty 

 substances are less soluble in formic acid than in acetic. 



The most striking results were obtained with fixation of Planaria 

 by a Zenker's fluid to which 5 parts of formic acid, instead of acetic, 

 was added just before using. The worms were allowed to become 

 extended and straightened on a glass slide in a very small amount of 

 water ; the fluid was pipetted on, and a No. 1 cover-slip dropped on. 

 After five minutes the cover-slip was removed and the specimens were 

 transferred to a vial containing the fluid. This method of killing 

 causes no writhing with tearing of the muscles, and produces no blister- 

 ing of the epidermis. The general histological details are excellent, 



